The use of a tailgate structure for domestic and industrial vehicles is well known in the art. For instance, tailgates are used with mining vehicles, such as coal haulers. Coal haulers receive coal, ore, and other materials from a vehicle, such as a continuous miner. The coal is then transported via the coal hauler to a dump point, such as a belt conveyor. The coal may be loaded onto the belt conveyor via a hopper with a feeder breaker.
In coal haulers, it is known to provide a tailgate which is hinged at the bottom, inside portion of the frame opening. The tailgate is held in an upright closed position by means of hydraulic cylinders. The coal hauler is loaded with the tailgate in the closed position and unloaded with the tailgate in the opened position.
Such prior art coal haulers suffer several disadvantages. With the tailgate extending beyond the mining vehicle body in an open position, the tailgate may become damaged when backing towards an ore receptacle or feeder apparatus. Additionally, while extending outwardly from the vehicle body, the tailgate is significantly exposed to the discharge stream of materials, thus increasing wear and damage to the tailgate. In addition, it is necessary to clean any remaining materials off of the opened tailgate.
It is also known to provide mining vehicles with a tailgate which is operated between a closed position and a position substantially above the mining vehicle. Such prior art tailgates operate adequately when discharging materials at a feeder or receptacle. However, when the vehicle is used to haul supplies, such as batteries, rock dust, or crib blocks, the size of the supplies to be hauled is limited to the clearance between the bottom of the raised tailgate and the bottom edge of the vehicle. In addition, the use of such vehicles is limited in mines where the overhead clearance is not sufficient to raise the tailgate to the fully opened position.
The prior art is replete with references for tailgate designs that can be operated in either a top-opening or a bottom-opening mode. Such "dual-opening mode" designs are frequently seen in connection with automobiles and refuse hauling and disposal vehicles. While functional for these and other types applications, such designs are not adaptable for use with mining vehicles.